Figure 2. Representative beating cell clusters and isolated cells.

A shows all the cells within the cluster contracting in synchrony suggesting entrainment of cells electrical activity. Note the typical pattern of growth that includes cells growing vertically. Arrow shows a common approach angle for patch electrode to a cell on the periphery of the beating cluster. B, single cells chosen for study, indicated by arrows, beat spontaneously and were roughly spherical with a slightly splayed, flat attachment to the coverslip. Both photographs acquired with 40× objective lens.